The present invention relates to a hub clutch device for connecting and disconnecting a drive axle and a wheel of a vehicle to and from each other.
As a conventional hub clutch device of the kind referred to above, there is one disclosed in, for example, Japanese Patent Laid-Open No. 60-151103. The hub clutch device is one in which a clutch mechanism for connecting and disconnecting an axle and a wheel of a four-wheel drive (4WD) vehicle to and from each other operates by an actuator.
The hub clutch device is arranged such that a flexible diaphragm forming an actuator is provided between the axle and a top portion of a housing, a pressure chamber is defined on the side of the axle, and an air chamber is defined on the side of the top portion of the housing.
The hub clutch device is arranged such that the clutch mechanism is connected and disconnected by deflection or flexure of the diaphragm due to pressure supply to the pressure chamber.
By the way, there is a fear that, since the air chamber is closed, malfunction occurs in the hub clutch device by a change in volume of the air chamber attendant upon a change in temperature due to a brake temperature, an outside air temperature and the like. Further, an operating pressure is also raised so that durability of a seal and the like is lowered.
In view of the above, an arrangement is disclosed in Japanese Patent Laid-Open No. SHO 61-238516 in which a return spring is arranged within the air chamber, and an air bore is provided for opening to the atmosphere, so that when the actuator operates, or a temperature changes, air can enter and exit through the air bore.
However, there is a fear that, as water or dust entering the air chamber through the air bore is frozen or solidified, the function of the hub clutch device may be lowered, or the hub clutch device may become inoperable, due to malfunction of the actuator.